Proper Refrigerant Charging

Proper refrigerant charging may be more important than you realize.

heating and cooling servicesIn times past, many residential hvac dealers and contractors have viewed spring and fall preseason maintenance primarily as an opportunity to keep their service technicians busy during the off-season.

The idea was to generate some income, give the techs some work, and hope to find a few units that need to be replaced.

However, current research is showing that the spring and fall preseason checkups are more important than many people once believed. Research by various industry organizations, including many engineers is showing that spring and fall checkups by a qualified technician can save the you the homeowner far more than the cost of the maintenance agreement.

If the technician does nothing more than check for an accurate charge, he can significantly impact operating efficiency and life expectancy of the system.

This research is demonstrating clearly that air conditioners truly are made up of matched components which must be fine-tuned and optimized to achieve proper performance.

First, let's look at the research by engineers and factory training center personnel. They placed a variety of air conditioning systems in controlled ambient rooms which are capable of simulating a wide range of operating conditions. They carefully monitored the operation of these systems as system charges were changed from significant under-charge to substantial over-charge.

Effects can vary.

These tests showed that the effects of improper charges can vary greatly from one system to another and from one set of operating conditions to another.

However, one conclusion was clear. The charge alone can have a substantial impact on system operation costs. A few percentage points of over-or-under-charge can raise electricity consumption significantly and shorten the life of the compressor.

Second, let's look at refrigerant from a technical standpoint. Basically, refrigerant serves three important functions in the operation of an air conditioning system.

  • Heat transfer. The refrigerant moves heat from inside the house to the outside.

  • Compressor cooling. It removes heat from the compressor motor windings.

  • Compressor lubrication. It circulates oil to lubricate the compressor.

Now let's look at the situation from your (the homeowner's) point of view. All of these functions are important to the proper operation of the cooling system. All three affect both the efficiency of operation and the durability of the compressor.

And, all of them are closely tied to the system's level of refrigerant charge. Here is what an under-or-over-charge can mean to you as the homeowner.

  • Reduced comfort. An improperly charged system will not dehumidify the air properly.

  • Poor heat transfer. An improperly charged system will not do its job of removing heat from inside the house and transferring it outside.

  • Reduced efficiency. Poor heat transfer results in increased power consumption. Refrigeration & Air Conditioning, published by the Air-Conditioning and Refrigeration Institute, cites this example of energy efficiency loss due to under-charging.

"At 100% of refrigeration charge, the EER (energy efficiency ratio was 8.4. With the undercharge at 95% of charge, an 8.1 EER resulted; at 90% 7.7; and at 85%, 6.75".

This means that a 15% under-charge can result in a 25% decrease in efficiency. As the charge drops farther, efficiency decreases faster - to 50% or more. Similar losses of efficiency result from over-charging the compressor.

  • Reduced reliability. A poorly charged system will not properly cool or lubricate the compressor. Those conditions will significantly shorten a compressor's life. That means extra expense - and aggravation - for you the homeowner.

  • Increased cost. The bottom line on system charging is that a poor charge - either over or under - costs the you homeowner money in both operating costs and maintenance expenses. 

Finally, let's look at what this information means to residential hvac dealers and contractors.

Basically, it means:

  • Our routine maintenance service is more than just work to keep our technicians busy in the off-season. It is an important service to our customers.

  • Finding and locating refrigerant leaks is more important than ever, even though virtually all residential air conditioning and heat pump systems use HCFCs (which are far less hazardous to the ozone layer than CFCs). If we recharge a leaking system without repairing the leak, the system's energy efficiency will begin dropping almost immediately.

  • We have the information needed to demonstrate to homeowners the importance of regular maintenance.

Most importantly, it means we owe it to our customers to offer them the opportunity to have their air conditioning and heat pump systems serviced as soon as possible.

And remember, this article deals with only one area of routine system maintenance. Other areas, such as cleaning the coils, can have similar impacts on the efficiency and operating life of any residential cooling system.